Sequential electronic switch



Oct. 4, 1960 H. T. MILLER 2,955,201

SEQUENTIAL ELECTRONIC SWITCH Filed Jan. 4, 195'! /2 C o/v TROLLED Lon oCONTROL. L. ED

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6 /3 0 -/00 l/ BIAS INVENTOR. HEN/Qy T MILLER L) T TOR/WE 45 UnitedStates Patent 2,955,201 SEQUENTIAL ELECTRONIC SWITCH Henry T. Miller,Honolulu, Hawaii, assignor to Collins Rfatllio Company, Cedar Rapids,Iowa, a corporation 0 owa Filed Jan. 4, 1957, Ser. No. 632,447

2 Claims. (Cl. 250-27) This invention relates to electronic switches andmore particularly to electronic switches for sequential operation.

It is well-known to control appropriate loads by ionizing gaseousdischarge tubes. This invention provides an electronic switching controlfor gaseous discharge tubes which permits rapid sequential control bythe tubes over various loads. One application of this invention uses thegaseous discharge tubes to provide clickless keying of amateur radioequipments. This keying is accomplished by having one gaseous dischargetube control the on-ofi operation of the receiver, and one gaseousdischarge tube control the on-off operation of the associatedtransmitter. The receiver and transmitter must be turned on and oif indesired sequences for break-in keying.

It is an object of this invention to control two loads with gaseousdischarge devices where the loads are to be turned on or ofl in desiredand predetermined sequences. It is a still further object of thisinvention to provide for two gaseous discharge devices with only onetiming circuit to control the sequential ionization and deionization ofthese discharge devices. It is still another object of this invention tocontrol two loads with gaseous discharge devices where only oneextinguishing means is required for extinguishing the two gaseousdischarge devices. It is another object of this invention to have theconduction or ionization period of gaseous discharge tubes controlledsimply and economically by one auxiliary tube and one timing circuit.

These and other objects of this invention will become apparent when thefollowing description is read in conjunction with the drawing, in whichthe single figure is a schematic diagram of one embodiment of thisinvention.

The controlled loads 4 and 5 in this invention may be any of the well'known electrical loads which are controllable by voltage such asrelays, heaters, lamps, etc. These loads control the on-oif operation ofother equipments such as transmitters and receivers. In one specificembodiment of this invention, relay circuits were used as the controlledloads 4 and 5. The relays or loads are operated when current flows inthe gaseous discharge is suflicient to cause the voltage applied to thegaseous discharge tubes 6 and 7 from the 300 v. source to be below theionization voltage. Thus, no current flows through tubes 6 and 7, andcontrolled loads 4 and 5 are open or closed as desired.

If switch 8 is now closed, bias voltage is gradually applied to the grid9 of the tube 11. This bias voltage is applied from the negative 100volt source through the resistance 13 to the grid 9. The gradual changesin the value of the bias voltage are due to the charging of thecapacitance 14. As the capacitance 14 is charged to a tubes 6 and 7respectively. When relays are used, this means that there is a currentflow in the winding of the relay to open or close the relay contacts.The switch 8 may be any switch means, or in a specific embodiment, itmay be a well-known thermostatic device or a wellknown telegraph key. Inoperation, when switch 8 is open, as shown in the drawing, no biasvoltage is applied to the grid 9 of the tube 11. It is to be noted thatother types of electron valves, such as transistors, for example, may beemployed in lieu of a vacuum tube 11. With no bias voltage applied tothe grid 9, tube 11 conducts, and thus current flows through tube 11.With tube 11 biased so as to conduct, and plate current flowing in tube11, there is a resultant heavy current flow through the resistance 12.When there is a heavy current flowing through resistance 12, the IR dropacross resistance 12 voltage equal to the cutofl bias value for grid 9of the tube 11, tube 11 ceases to conduct. As tube 11 doesnot cease toconduct instantaneously, the IR drop across resistance 12 decreases andthe voltagerises gradually along the resistance 12. The ionizationvoltage of tube 6 is reached first as the voltage along resistance 12changes, and tube 6 ionizes and conducts. Subsequently, the ionizationvoltage of tube 7 will be reached as the voltage alongv the resistance12 rises, and it also will conduct. The time between the ionization ofthe two tubes will actually be controlled by the time constant of thecharging circuit.

Now when the switch 8 is opened, the capacitance 14 and the resistance15 form a discharge circuit. The voltage which was applied to the grid 9will deteriorate slowly due to the time constant of the dischargecircuit. This reduction in bias voltage will cause gradual conduction inthe tube 11. Conduction by tube 11 will result in current flow throughresistance 12. As current flows through resistance 12, the IR drop inthe resistance will become greater, and the voltage applied to the tubes6 and 7 will deteriorate below the value necessary for ionization of thetubes. As a result of this gradually lowered voltage along resistance12, tube 7 will be extinguished first. Tube 6 will subsequently beextinguished with the time interval dependent upon the time constant ofthe resistance capacitance circuit including resistance 15 andcapacitance 14.

It is obvious that this arrangement can provide clickfree keying wherethe receiver is turned off by depressing key 8,'and the transmitter issubsequently turned on. As the key is released, the transmitter goes offfirst, and the receiver is subsequently turned on.

Although this invention has been described with respect to a particularembodiment thereof, it is not to be so limited as changes andmodifications may be made therein which are within the full intendedscope of the invention as defined by the appended claims.

What is claimed is:

1. A sequential switching circuit comprising an electron valve havingelectron collector means, control electrode means, and electron emittingmeans, bias voltage source means, switching means for supplying the biasvoltage of said bias voltage source means to said control electrodemeans to cut oif said electron valve, time delay means for delaying achange of potential of said control electrode means, electron collectorvoltage supply means, electron collector load impedance means connectedbetween said electron collector means and said electron collectorvoltage supply means, a plurality of gaseous discharge devices eachcomprising a cathode electrode and an anode electrode, similar ones ofsaid electrodes of said gaseous discharge devices being connected atdifferent points on said electron collector load impedance means so thatas the current through said electron collectorload impedance meansdecreases as said electron valve becomes nonconductive one of saidgaseous discharge devices will become conductive and then a shortinterval of time later another of said gaseous discharge devices willbecome conductive so that both gaseous discharge devices are in aconductive condition and as the current through said electron collectorload impedance'means increases as the electron valve becomes conductivesaid other gaseous discharge device will become nonconductive and then ashort interval of time later the said one of said gaseous dischargedevices will become nonconductive so that both gaseous discharge devicesare in a nonconductive condition.

2. A sequential switching circuit comprising an electron valve havingelectron collector means, control electrode means, and electron emittingmeans, a bias voltage source means, switching means for supplying thebias voltage of said bias voltage source means to said control electrodemeans to control the conduction of said electron valve, time delay meansfor delaying a change of potential of said control electrode means, saidtime delay means comprising a parallel circuit arrangement of capacitiveand resistive means connected between said control electrode means andsaid electron emitting means of said valve, electron collector voltagesupply means, an electron collector load impedance means connectedbetween said electron collector means and said electron collector supplymeans, first and second gaseous discharge devices each comprising acathode electrode and an anode electrode, controlled load meansconnected to the cathode electrodes of said first and second dischargedevices, the anode electrode of said first discharge device beingconnected to a variable tap on said electron collector load impedancemeans, and the anode electrode of said second discharge device beingconnected to said electron collector means so that as the currentthrough said electron collector load impedance means decreases as saidelectron valve becomes nonconductive said first discharge device willbecome conductive and then a short interval of time later said seconddischarge device will become conductive so that both discharge devicesare in a conductive condition, and as the current through said electroncollector load impedance meansincreases as said electron valve becomesconductive, said second discharge device will become nonconductive andthen a short interval of time later, said first discharge device willbecome nonconductive, so that both discharge devices are in anonconductive condition.

References Cited in the file of this patent UNITED STATES PATENTS1,728,745 Brown et al Sept. 17, 1929 2,095,124 Cockrell Oct. 5, 19372,298,695 Hall Oct. 13, 1942 2,684,440 Wallace et al July 20, 1954 OTHERREFERENCES CQ, May 1948, pages 37, 38 article, Clickless Keying Using VRTubes, by Mack Seybold.

Pub. L Time Delay Circuits, The C-D Capacitor, vol. 17, No. 3, March1952, page 7.

